Semiconductor device and method of manufacturing the same

ABSTRACT

In one embodiment, a semiconductor device includes a first interconnection including a first extending portion extending in a first direction, and a first curved portion curved with respect to the first extending portion. The device further includes a second interconnection including a second extending portion extending in the first direction and adjacent to the first extending portion in a second direction, and a second curved portion curved with respect to the second extending portion. The device further includes a first plug provided on the first curved portion, or on a first non-opposite portion included in the first extending portion and not opposite to the second extending portion in the second direction. The device further includes a second plug provided on the second curved portion, or on a second non-opposite portion included in the second extending portion and not opposite to the first extending portion in the second direction.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2018-051475, filed on Mar. 19, 2018, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate to a semiconductor device and a method of manufacturing the same.

BACKGROUND

When a plug is formed on an interconnection of a semiconductor device, the plug is typically formed on a pad included in the interconnection in order to make it easier to form the plug at a correct position. However, because such a pad makes it difficult to reduce the size of the semiconductor device, it is desirable that the plug can be appropriately and easily formed without using the pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view illustrating a structure of a semiconductor device in a first embodiment;

FIG. 2 is a cross-section view illustrating a structure of a columnar portion in the first embodiment;

FIG. 3 is a cross-section view illustrating a method of manufacturing the semiconductor device in the first embodiment;

FIG. 4 is a cross-section view for explaining a structure in the vicinity of a bit line in the first embodiment;

FIG. 5 is a plan view for explaining the structure and the manufacturing method of the semiconductor device in the first embodiment;

FIG. 6 is a plan view for explaining a structure and a manufacturing method of a semiconductor device in a second embodiment; and

FIG. 7 is a plan view for explaining a structure and a manufacturing method of a semiconductor device in a third embodiment.

DETAILED DESCRIPTION

Embodiments will now be explained with reference to the accompanying drawings.

In one embodiment, a semiconductor device includes a first interconnection including a first extending portion that extends in a first direction, and a first curved portion that is curved with respect to the first extending portion. The device further includes a second interconnection including a second extending portion that extends in the first direction and is adjacent to the first extending portion in a second direction perpendicular to the first direction, and a second curved portion that is curved with respect to the second extending portion. The device further includes a first plug provided on the first curved portion, or provided on a first non-opposite portion that is included in the first extending portion and is not opposite to the second extending portion in the second direction. The device further includes a second plug provided on the second curved portion, or provided on a second non-opposite portion that is included in the second extending portion and is not opposite to the first extending portion in the second direction.

First Embodiment

FIG. 1 is a cross-section view illustrating a structure of a semiconductor device in a first embodiment. The semiconductor device in FIG. 1 is a three-dimensional memory in which an array chip 1 and a circuit chip 2 are pasted. The array chip 1 is an example of a first chip, and the circuit chip 2 is an example of a second chip.

The array chip 1 includes a memory cell array 11 including a plurality of memory cells, an insulating layer 12 (for example, a silicon nitride film) on the memory cell array 11, an insulating layer 13 (for example, a silicon oxide film) on the insulating layer 12, and an inter layer dielectric 14 under the memory cell array 11.

The circuit chip 2 is provided under the array chip 1 via an insulating layer 15. The circuit chip 2 includes an inter layer dielectric 16 and a substrate 17 under the inter layer dielectric 16. The substrate 17 is, for example, a semiconductor substrate such as a silicon substrate. FIG. 1 illustrates an X direction and a Y direction which are parallel to a surface of the substrate 17 and which are perpendicular to each other, and a Z direction which is perpendicular to the surface of the substrate 17. In the present specification, while a +Z direction is handled as an upward direction, and a −Z direction is handled as a downward direction, the −Z direction may match a gravity direction or does not have to match the gravity direction. A ±Y direction is an example of a first direction, and a ±X direction is an example of a second direction.

The array chip 1 includes a plurality of word lines WL, a back gate BG and a selector gate SG as an electrode layer within the memory cell array 11. FIG. 1 illustrates a step-like structure portion 21 of the memory cell array 11. As illustrated in FIG. 1, each word line WL is electrically connected to a word interconnection layer 23 via a contact plug 22, the back gate BG is electrically connected to a back gate interconnection layer 25 via a contact plug 24, and the selector gate SG is electrically connected to a selector gate interconnection layer 27 via a contact plug 26. The columnar portion CL which pierces through the word lines WL, the back gate BG and the selector gate SG is electrically connected to bit lines BL via plugs 28.

The circuit chip 2 includes a plurality of transistors 31. Each transistor 31 includes a gate electrode 32 provided on the substrate 17 via a gate insulator, and a source diffusion layer and a drain diffusion layer which are provided within the substrate 17 and which are not illustrated. The circuit chip 2 further includes a plurality of plugs 33 provided on the source diffusion layers or the drain diffusion layers of the transistors 31, an interconnection layer 34 including a plurality of interconnections, provided on these plugs 33, and an interconnection layer 35 including a plurality of interconnections provided on the interconnection layer 34. A plurality of metal pads 36 provided within the insulating layer 15 are provided on the interconnection layer 35. The array chip 1 includes an interconnection layer 37 including a plurality of interconnections, provided on these metal pads 36. Each word line WL of the present embodiment is electrically connected to the interconnection layer 37.

The array chip 1 further includes a pad 38 electrically connected to the interconnection layer 37 via a via plug which is not illustrated, an external connection electrode 39 provided on the pad 38, and an external connection pad 40 provided on the external connection electrode 39. The external connection pad 40 can be connected to a mounted substrate or other apparatuses via a solder ball, a metal bump, a bonding wire, or the like.

FIG. 2 is a cross-section view illustrating a structure of a columnar portion CL in the first embodiment.

As illustrated in FIG. 2, the memory cell array 11 includes a plurality of word lines WL and a plurality of insulating layers 41 which are alternately laminated on the inter layer dielectric 14. Each word line WL is, for example, a W (tungsten) layer. Each insulating layer 41 is, for example, a silicon oxide film.

The columnar portion CL includes a block insulator 42, a charge accumulating layer 43, a tunnel insulator 44, a channel semiconductor layer 45 and a core insulator 46. The charge accumulating layer 43, which is, for example, a silicon nitride film, is formed on a side face of the word lines WL and the insulating layer 41 via the block insulator 42. The channel semiconductor layer 45, which is, for example, a silicon layer, is formed on a side face of the charge accumulating layer 43 via the tunnel insulator 44. The block insulator 42, the tunnel insulator 44 and the core insulator 46 are, for example, a silicon oxide film and a metal insulator.

FIG. 3 is a cross-section view illustrating a method of manufacturing the semiconductor device in the first embodiment.

FIG. 3 illustrates an array wafer W1 including a plurality of array chips 1, and a circuit wafer W2 including a plurality of circuit chips 2. FIG. 3 further illustrates a first insulating layer 47 and a plurality of first metal pads 49 provided on a lower face of the array wafer W1, and a second insulating layer 48 and a plurality of second metal pads 50 provided on an upper face of the circuit wafer W2. Each of the first metal pads 49 is provided on a lower face of the interconnection layer 37, and each of the second metal pads 50 is provided on an upper face of the interconnection layer 35. The first and the second metal pads 49 and 50 are respectively examples of first and the second pads. Further, the array wafer W1 includes a substrate 18 on the insulating layer 13.

While, in FIG. 3, the first insulating layer 47 is formed on a lower face of the inter layer dielectric 14, the first insulating layer 47 may be included in and integrated with the inter layer dielectric 14. In a similar manner, while, in FIG. 3, the second insulating layer 48 is formed on an upper face of the inter layer dielectric 16, the second insulating layer 48 may be included in and integrated with the inter layer dielectric 16. In this case, the surfaces of the inter layer dielectrics 14 and 16 are modified through plasma, or the like.

First, the array wafer W1 and the circuit wafer W2 are pasted with mechanical pressure. By this means, the first insulating layer 47 adheres to the second insulating layer 48, so that the insulating layer 15 is formed. Then, the array wafer W1 and the circuit wafer W2 are annealed at 400° C. By this means, the first metal pad 49 is bonded to the second metal pad 50, so that a plurality of metal pads 36 are formed.

Subsequently, the substrate 18 is removed through CMP (Chemical Mechanical Polishing) or wet etching, and the array wafer W1 and the circuit wafer W2 are cut into a plurality of chips. In this manner, the semiconductor device in FIG. 1 is manufactured. The external connection electrode 39 and the external connection pad 40 are formed on the pad 38 after the substrate 18 is removed.

Details of a structure in the vicinity of the metal pad 36 and the interconnection layer 37 will be described later with reference to FIG. 4, or the like.

FIG. 4 is a cross-section view for explaining a structure in the vicinity of the bit line BL in the first embodiment.

In a similar manner to FIG. 1, FIG. 4 illustrates the columnar portion CL, the plug 28, the bit line BL, the interconnection layer 37 and the metal pad 36. However, it should be noted that an upward direction and a downward direction in FIG. 4 are inverse with respect to an upward direction and a downward direction in FIG. 1. FIG. 4 illustrates a state where the semiconductor device in FIG. 1 is made upside down. This will also similarly apply to FIG. 5 to FIG. 7 which will be described later.

The plug 28 includes a contact plug 52 provided on the columnar portion CL, and a lower via plug 51 provided on the contact plug 52, and the bit line BL is provided on the lower via plug 51. The semiconductor device of the present embodiment further includes an upper via plug 61 provided on the bit line BL, and an interconnection inside the interconnection layer 37 is provided on the upper via plug 61. The semiconductor device of the present embodiment further includes a via plug 62 provided on this interconnection, and the metal pad 36 is provided on the via plug 62. The metal pad 36 includes a first metal pad 49 provided on the via plug 62 and a second metal pad 50 provided on the first metal pad 49.

The semiconductor device of the present embodiment includes a plurality of sets of structures illustrated in FIG. 4, and each structure includes the columnar portion CL, the contact plug 52, the lower via plug 51, the bit line BL, the upper via plug 61, the interconnection inside the interconnection layer 37, the via plug 62, and the metal pad 36. Examples of such a lower via plug 51, a bit line BL and an upper via plug 61 will be described later with reference to FIG. 5 to FIG. 7.

FIG. 5 is a plan view for explaining a structure and a manufacturing method of the semiconductor device in the first embodiment.

FIG. 5 illustrates twelve bit lines BL, twelve lower via plugs 51 provided under the bit lines BL, and twelve upper via plugs 61 provided on the bit lines BL. For example, the bit lines BLa to BLd are respectively electrically connected to the lower via plugs 51 a to 51 d and the upper via plugs 61 a to 61 d.

These bit lines BL can be formed by, for example, cutting six circular interconnections (loop interconnections) 71 at cutting positions 72. Further, these circular interconnections 71 can be formed by, for example, forming circular interconnections 71 on side faces of a plurality of cores extending in the Y direction and removing the cores thereafter. In FIG. 5, a circular interconnection 71 a is cut at a cutting position 71 a and a cutting position 71 b, and a circular interconnection 71 b is cut at the cutting position 71 b and a cutting position 71 c.

As a result, each circular interconnection 71 is cut into two bit lines BL including an extending portion 73 extending in the Y direction in an extending shape (for example, in a straight-line shape) and a curved portion 74 curved with respect to the extending portion 73. While the curved portion 74 in the present embodiment extends from the extending portion 73 in a curved-line shape (for example, in a U shape or in a 3 shape), the curved portion 74 may extend from the extending portion 73 in an extending shape if the curved portion 74 is curved with respect to the extending portion 73. For example, the curved portion 74 may extend in the X direction from the extending portion 73 in an extending shape. The extending portion 73 and the curved portion 74 are examples of linear portions, and each bit line BL is an example of an interconnection including linear portions.

For example, a bit line BLa includes an extending portion 73 a extending in the Y direction and a curved portion 74 a curved with respect to the extending portion 73 a. A bit line BLb includes an extending portion 73 b extending in the Y direction and adjacent to the extending portion 73 a in the X direction and a curved portion 74 b curved with respect to the extending portion 73 b. A bit line BLc includes an extending portion 73 c extending in the Y direction and adjacent to the extending portion 73 b in the X direction and a curved portion 74 c curved with respect to the extending portion 73 c. A bit line BLd includes an extending portion 73 d extending in the Y direction and adjacent to the extending portion 73 c in the X direction and a curved portion 74 d curved with respect to the extending portion 73 d. This will also similarly apply to other bit lines BL. The bit lines BLa to BLd are respectively examples of first to fourth interconnections. Further, the ±Y direction is an example of a first direction, and the ±X direction is an example of a second direction.

Because the bit line BLa and the bit line BLb are formed from the same circular interconnection 71 a, the curved portion 74 a is curved on the extending portion 73 b side with respect to the extending portion 73 a, and the curved portion 74 b is curved on the extending portion 73 a side with respect to the extending portion 73 b. In a similar manner, because the bit line BLc and the bit line BLd are formed from the same circular interconnection 71 b, the curved portion 74 c is curved on the extending portion 73 d side with respect to the extending portion 73 c, and the curved portion 74 d is curved on the extending portion 73 c side with respect to the extending portion 73 d.

FIG. 5 illustrates a width W1 of each extending portion 73, a width W2 between the extending portions 73, and a width W3 of each cutting position 72. For example, the width W2 has a length as long as the width W1, and the width W3 has a length approximately four times as long as the width W1 or the width W2.

In the present embodiment, a film (not illustrated) for etching is formed on the circular interconnections 71, a plurality of openings are formed in this film, and each circular interconnection 71 is cut into two bit lines BL through etching using these openings. Examples of the above-described film can include a resist film and a hard mask film. The cutting positions 72 in FIG. 5 correspond to these openings. Therefore, the respective openings are formed on the two circular interconnections 71 (more specifically, on the two extending portions 73) as illustrated in FIG. 5.

If the respective openings are formed on one extending portion 73, while the width W3 of each opening becomes ½, with such narrow openings, it is difficult to process or align the openings. However, because, in the present embodiment, the respective openings are formed on two extending portions 73, it is possible to alleviate this problem. In the present embodiment, the cutting position (opening) 71 a is provided on the extending portion 72 a and on an extending portion adjacent to the extending portion 72 a, the cutting position 71 b is provided on the extending portion 72 b and on the extending portion 72 c, and the cutting position 71 c is provided on the extending portion 72 d and on an extending portion adjacent to the extending portion 72 d.

The upper via plugs 61 a to 61 d are respectively provided on the curved portions 74 a to 74 d instead of being provided on the extending portions 73 a to 73 d. A width of the curved portion 74 is approximately three times as wide as the width W1 of the extending portion 73. Therefore, according to the present embodiment, by forming the upper via plugs 61 on the curved portions 74, it is possible to easily form the upper via plugs 61 at correct positions compared to a case where the upper via plugs 61 are formed on the extending portions 73. Meanwhile, the lower via plugs 51 a to 51 d are respectively provided under the extending portions 73 a to 73 d. This will also similarly apply to other bit lines BL.

FIG. 5 illustrates a gap Ga between one end portion of the bit line BLa and one end portion of the bit line BLb, and a gap Gb between the other end portion of the bit line BLa and the other end portion of the bit line BLb. Further, FIG. 5 illustrates a gap Gc between one end portion of the bit line BLc and one end portion of the bit line BLd, and a gap Gd between the other end portion of the bit line BLc and the other end portion of the bit line BLd.

These gaps Ga and Gb are formed by cutting each circular interconnection 71 at two cutting positions 72. Therefore, the gap Gb is located within the cutting position 72 a, the gaps Ga and Gd are located within the cutting position 72 b, and the gap Gc is located within the cutting position 72 c. Because the gaps Ga and Gd are both located within the cutting position 72 b, the gap Gd is located in the X direction of the gap Ga. The cutting position 72 a is an example of a first opening, the gap Gb is an example of a first portion for cutting, and a gap adjacent to the gap Gb is an example of a third portion for cutting. Further, the cutting position 72 b is an example of a second opening, the gap Ga is an example of a second portion for cutting, and the gap Gd is an example of a fourth portion for cutting.

The above-described structure is similar in other bit lines BL. The bit lines BL in the present embodiment are configured such that structures similar to those of the bit lines BLa to BLd are periodically repeated in the X direction.

The upper via plugs 61 a to 61 d may be respectively provided in the +X direction or the −X direction of the gaps Ga to Gd on the extending portions 73 a to 73 d, i.e., may be respectively provided on non-opposite portions of the extending portions 73 a to 73 d. The non-opposite portions are provided such that a non-opposite portion of an extending portion of an interconnection is not opposite to an extending portion of an adjacent interconnection in the +X direction or the −X direction. Also in this case, it becomes possible to easily form the upper via plugs 61 at correct positions. Details of such upper via plugs 61 will be described later with reference to FIG. 6.

As described above, the upper via plugs 61 of the present embodiment are formed on the curved portions 74 of the bit lines BL. Therefore, according to the present embodiment, it becomes possible to appropriately and easily form the upper via plugs 61 on the bit lines BL.

Further, in the present embodiment, although the upper via plugs 61 are formed on the bit lines BL, the upper via plugs 61 can be easily brought into contact with the bit lines BL in a wide area. Therefore, according to the present embodiment, it becomes possible to reduce contact resistance between the upper via plugs 61 and the bit lines BL.

Further, in the present embodiment, it becomes not necessary to form pads within the interconnection layer including the bit lines BL, the upper via plugs 61 are directly formed on the bit lines BL instead of being formed on the pads. Therefore, according to the present embodiment, it becomes possible to make the semiconductor device smaller by omitting such pads.

The upper via plugs 61 of the present embodiment may be provided on the extending portions 73 or on the curved portions 74. By this means, it is possible to make it unnecessary to form pads within the interconnection layer including the bit lines BL. However, in the case where the bit lines BL are thin, it becomes difficult to form the upper via plugs 61 at correct positions on the extending portions 73. For example, if misalignment between positions of the extending portions 73 and positions of the upper via plugs 61 occurs, there is a possibility that short circuits between the extending portions 73 or poor connection between the extending portions 73 and the upper via plugs 61 may occur. The bit lines BL tend to be thinner as a result of a three-dimensional structure being employed as a structure of a memory instead of a two-dimensional structure being employed and by the memory being formed through pasting process, which makes it more likely to cause short circuits and poor connection. Therefore, the upper via plugs 61 of the present embodiment are preferably provided on the curved portions 74 rather than being provided on the extending portions 73. Meanwhile, in the case where it is possible to suppress short circuits and poor connection, the upper via plugs 61 of the present embodiment can be provided on the extending portions 73.

Second Embodiment

FIG. 6 is a plan view for explaining a structure and a manufacturing method of a semiconductor device in a second embodiment.

The semiconductor device of the present embodiment has a structure similar to that of the semiconductor device in the first embodiment. However, an area of an upper face and an area of a lower face of each of the upper via plugs 61 of the present embodiment are respectively set larger than an area of an upper face and an area of a lower face of each of the lower via plugs 51. In FIG. 6, the upper face and the lower face of each of the upper via plugs 61 are respectively surfaces in the +Z direction and the −Z direction of each of the upper via plugs 61. In a similar manner, the upper face and the lower face of each of the lower via plugs 51 are respectively surfaces in the +Z direction and the −Z direction of each of the lower via plugs 51.

Further, an upper via plug 61 a of the present embodiment is provided in the +X direction of the gap Ga on the extending portion 73 a, and an upper via plug 61 b of the present embodiment is provided in the −X direction of the gap Gb on the extending portion 73 b. See FIG. 5 regarding details of positions of the gaps Ga and Gb. Meanwhile, upper via plugs 61 c and 61 d of the present embodiment are respectively provided on curved portions 74 c and 74 d in a similar manner to the first embodiment. In the present embodiment, such a structure is periodically repeated in the X direction.

Because the areas of the lower faces of the upper via plugs 61 of the present embodiment are large, there is an advantage that the upper via plugs 61 can be easily formed on the bit lines BL. Meanwhile, because the areas of the lower face and the upper face of the upper via plugs 61 of the present embodiment are large, if arrangement similar to that of the upper via plugs 61 in the first embodiment is employed as arrangement of the upper via plugs 61 of the present embodiment, there is a possibility that the upper via plug 61 a contacts the upper via plug 61 d or a possibility that the upper via plug 61 b contacts the upper via plug 61 c.

Therefore, the upper via plugs 61 a and 61 b of the present embodiment are respectively provided in the +X direction or in the −X direction of the gaps Ga and Gb on the extending portions 73 a and 73 b. Therefore, according to the present embodiment, it is possible to appropriately and easily form the upper via plugs 61 on the bit lines BL while avoiding the upper via plugs 61 from contacting each other.

Third Embodiment

FIG. 7 is a plan view for explaining a structure and a manufacturing method of a semiconductor device in a third embodiment. Concerning the present embodiment, differences with the first and the second embodiments will be mainly described, and features in common with the first and the second embodiments will be omitted.

The bit lines BL of the present embodiment can be formed by cutting six circular interconnections (loop interconnections) 81 at cutting positions 82. Further, these circular interconnections 81 can be formed by forming a plurality of second cores on side faces of a plurality of first cores extending in the Y direction, removing the first cores thereafter, forming the circular interconnections 81 on the side faces of the second cores, and removing the second cores thereafter. In FIG. 7, a circular interconnection 81 a is cut at a cutting position 82 a and a cutting position 82 b, and a circular interconnection 81 b is also cut at the cutting position 82 a and the cutting position 82 b. The circular interconnection 81 b surrounds the circular interconnection 81 a, and this will also similarly apply to other circular interconnections 81.

As a result, each circular interconnection 81 is divided into two bit lines BL including an extending portion 83 extending in the Y direction in an extending shape, and a curved portion 84 curved with respect to the extending portion 83. While the curved portion 84 of the present embodiment extends from the extending portion 83 in a curved-line shape (for example, in a U shape or in a 3 shape), the curved portion 84 may extend from the extending portion 83 in an extending shape if the curved portion 84 is curved with respect to the extending portion 83. For example, the curved portion 84 may extend in the X direction from the extending portion 83 in an extending shape. The extending portion 83 and the curved portion 84 are examples of linear portions, and each bit line BL is an example of an interconnection including the linear portions.

For example, a bit line BLb includes an extending portion 83 b extending in the Y direction, and a curved portion 84 b curved with respect to the extending portion 83 b. A bit line BLc includes an extending portion 83 c extending in the Y direction and adjacent to the extending portion 83 b in the X direction, and a curved portion 84 c curved with respect to the extending portion 83 c. The bit lines BLb and BLc are formed from a circular interconnection 81 a. Further, a bit line BLa includes an extending portion 83 a extending in the Y direction and adjacent to the extending portion 83 b in the −X direction, and a curved portion 84 a curved with respect to the extending portion 83 a. A bit line BLd includes an extending portion 83 d extending in the Y direction and adjacent to the extending portion 83 c in the X direction, and a curved portion 84 d curved with respect to the extending portion 83 d. The bit lines BLa and BLd are formed from a circular interconnection 81 b. This will also similarly apply to other bit lines BL. The bit lines BLb, BLc, BLa and BLd of the present embodiment are respectively examples of first to fourth interconnections.

Because the bit line BLb and the bit line BLc are formed from the same circular interconnection 81 a, the curved portion 84 b is curved on the extending portion 83 c side with respect to the extending portion 83 b, and the curved portion 84 c is curved on the extending portion 83 b side with respect to the extending portion 83 c. In a similar manner, because the bit line BLa and the bit line BLd are formed from the same circular interconnection 81 b, the curved portion 84 a is curved on the extending portion 83 d side with respect to the extending portion 83 a, and the curved portion 84 d is curved on the extending portion 83 a side with respect to the extending portion 83 d. Further, because the circular interconnection 81 b surrounds the circular interconnection 81 a, radii of curvature of the curved portions 84 a and 84 d are greater than radii of the curved portions 84 b and 84 c.

In the present embodiment, a film (not illustrated) for etching is formed on the circular interconnections 81, a plurality of openings are formed in this film, and each circular interconnection 81 is cut into two bit lines BL through etching using these openings. Examples of the above-described film can include a resist film and a hard mask film. The cutting positions 82 in FIG. 7 correspond to these openings. Therefore, the respective openings are formed on two circular interconnections 81 (more specifically, on two extending portions 83) as illustrated in FIG. 7.

The semiconductor device of the present embodiment includes a gap Gb between one end portion of the bit line BLb and one end portion of the bit line BLc within the cutting position 82 b, and includes a gap Gc between the other end portion of the bit line BLb and the other end portion of the bit line BLc within the cutting position 82 a. The semiconductor device of the present embodiment further includes a gap Ga between one end portion of the bit line BLa and one end portion of the bit line BLd within the cutting position 82 b and includes a gap Gd between the other end portion of the bit line BLa and the other end portion of the bit line BLd within the cutting position 82 a.

These gaps Ga and Gb are formed by cutting each circular interconnection 81 at two cutting positions 82. Therefore, the gaps Ga and Gb are located within the cutting position 82 b, and the gaps Gc and Gd are located within the cutting position 82 a. Because the gaps Ga and Gb are both located within the cutting position 82 b, the gap Ga is located in the X direction of the gap Gb. Because the gaps Gc and Gd are both located within the cutting position 82 a, the gap Gc is located in the X direction of the gap Gd. The cutting position 82 b of the present embodiment is an example of a first opening, the gap Gb is an example of a first portion for cutting, and the gap Ga is an example of a third portion for cutting. Further, the cutting position 82 a of the present embodiment is an example of a second opening, the gap Gc is an example of a second portion for cutting, and the gap Gd is an example of a fourth portion for cutting.

In the present embodiment, the upper via plug 61 b is provided in the −X direction of the gaps Ga and Gb on the extending portion 83 b, and the upper via plug 61 c is provided in the +X direction of the gaps Gc and Gd on the extending portion 83 c. Further, the upper via plug 61 a is provided on the curved portion 84 a, and the upper via plug 61 d is provided on the curved portion 84 d. Therefore, according to the present embodiment, in a similar manner to the first and the second embodiments, it becomes possible to easily form these upper via plugs 61 at correct positions. This will also similarly apply to other bit lines BL.

A right arrow on the upper via plug 61 a indicates a case where a position where the upper via plug 61 a is formed is displaced in a direction of arrow (+X direction). Because the upper via plug 61 a of the present embodiment is located on a right side of a top of the curved portion 84 a, short circuits are less likely to occur even if such displacement occurs. In a similar manner, because the upper via plug 61 d of the present embodiment is located on a right side of a top of the curved portion 84 d, short circuits are less likely to occur even if such displacement occurs. Therefore, such arrangement of the upper via plugs 61 a and 61 d is effective, for example, in the case where positions where the upper via plugs 61 a and 61 d are formed tend to be displaced in the +X direction. On the other hand, in the case where the positions where the upper via plugs 61 a and 61 d are formed tend to be displaced in the −X direction, the upper via plugs 61 a and 61 d may be disposed on a left side of the tops of the curved portions 84 a and 84 d.

The above-described structure will also similarly apply to other bit lines BL. The bit lines BL of the present embodiment are configured such that structures similar to those of the bit lines BLa to BLd are periodically repeated in the X direction.

As described above, the upper via plugs 61 of the present embodiment are formed on the curved portions 84 of the bit lines BL or formed on the extending portions 83 of the bit lines BL so as to be adjacent to gaps between the bit lines BL. Therefore, according to the present embodiment, it becomes possible to appropriately and easily form the upper via plugs 61 on the bit lines BL in a similar manner to the first and the second embodiments.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel devices and methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the devices and methods described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 

The invention claimed is:
 1. A semiconductor device comprising: a first interconnection including a first extending portion that extends in a first direction, and a first curved portion that is curved with respect to the first extending portion; a second interconnection including a second extending portion that extends in the first direction and is adjacent to the first extending portion in a second direction perpendicular to the first direction, and a second curved portion that is curved with respect to the second extending portion; a first plug provided on the first curved portion, or provided on a first non-opposite portion that is included in the first extending portion and is not opposite to the second extending portion in the second direction; and a second plug provided on the second curved portion, or provided on a second non-opposite portion that is included in the second extending portion and is not opposite to the first extending portion in the second direction.
 2. The device of claim 1, wherein the first curved portion is curved on the second extending portion side with respect to the first extending portion, and the second curved portion is curved on the first extending portion side with respect to the second extending portion.
 3. The device of claim 1, further comprising: a first lower plug provided under the first extending portion; and a second lower plug provided under the second extending portion, wherein an area of an upper face and an area of a lower face of the first plug are respectively larger than an area of an upper face and an area of a lower face of the first lower plug, and an area of an upper face and an area of a lower face of the second plug are respectively larger than an area of an upper face and an area of a lower face of the second lower plug.
 4. The device of claim 1, further comprising: a third interconnection including a third extending portion that extends in the first direction and is adjacent to the second extending portion in the second direction, and a third curved portion that is curved with respect to the third extending portion; a fourth interconnection including a fourth extending portion that extends in the first direction and is adjacent to the third extending portion in the second direction, and a fourth curved portion that is curved with respect to the fourth extending portion; a third plug provided on the third curved portion, or provided on a third non-opposite portion that is included in the third extending portion and is not opposite to the fourth extending portion in the second direction; and a fourth plug provided on the fourth curved portion, or provided on a fourth non-opposite portion that is included in the fourth extending portion and is not opposite to the third extending portion in the second direction, wherein the fourth non-opposite portion is located in the second direction of the first non-opposite portion.
 5. The device of claim 1, further comprising: a third interconnection including a third extending portion that extends in the first direction and is adjacent to the first extending portion in the second direction, and a third curved portion that is curved with respect to the third extending portion; a fourth interconnection including a fourth extending portion that extends in the first direction and is adjacent to the second extending portion in the second direction, and a fourth curved portion that is curved with respect to the fourth extending portion; a third plug provided on the third curved portion; and a fourth plug provided on the fourth curved portion.
 6. The device of claim 5, wherein the third curved portion is curved on the fourth extending portion side with respect to the third extending portion, and the fourth curved portion is curved on the third extending portion side with respect to the fourth extending portion.
 7. The device of claim 5, wherein a radius of curvature of the third curved portion is greater than a radius of curvature of the first curved portion, and a radius of curvature of the fourth curved portion is greater than a radius of curvature of the second curved portion.
 8. The device of claim 5, wherein the first plug is provided on the first non-opposite portion and the third non-opposite portion, and the second plug is provided on the second non-opposite portion and the fourth non-opposite portion. 